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We have on arlberg in /etc/sysctl.conf

# increase Linux TCP buffer limits
net.core.rmem_max = 10485760
net.core.wmem_max = 10485760
net.core.netdev_max_backlog=100000

# increase Linux autotuning TCP buffer limits
# min, default, and max number of bytes to use
net.ipv4.tcp_mem = 382401 509869 764802
net.ipv4.tcp_rmem = 4096 131072	6291456
net.ipv4.tcp_wmem = 4096 16384 4194304

# increase Linux autotuning UDP buffer limits
net.ipv4.udp_mem = 764178 1018904 1528356

Some network equipment testers screw the values up to:

Linux kernel (Socket buffers)
net.core.rmem_max=1342177280(default 131071)
net.core.wmem_max=516777216 (default 131071)
net.core.rmem_default=10000000(default 129024)
net.core.wmem_default=10000000(default 129024)
net.core.netdev_max_backlog=416384 (default 1000)
net.core.optmem_max= 524288 (default 20480)
net.ipv4.udp_mem = 11416320 15221760 22832640     (default 262144 327680 393216)